There is a considerable and ever-increasing demand for "ersatz" or substitute wood-based products for utilization in place of the natural goods. This is particularly so in fields where particularly high strength and/or precisely-dimensioned, high quality-type goods are not involved. These, in other words, constitute relatively "rough"-type wood products and materials of construction.
Natural wood and lumber for such "rough" character applications (such as, aspen, poplar--or "popple", as it is sometimes called--, spruce, cottonwood, dogwood, jackpine, some maples and other relatively low-quality or low-grade stock) is becoming increasingly expensive, even though of a more-or-less "junk" wood reputation. Primarily for this reason of cost, it is getting less attractive and satisfactory for many applications and uses wherein it previously was entirely satisfactory from both performance and economics oriented points of view.
A good illustration of this are the separators used by brick manufacturers to maintain truck-lift openings in the brick cubes utilized for handling and storage. These at least historically were widely made of poplar slats of typical dimensions of about 1/4".times.4-6".times.28-32". Their cost, at one time, was quite reasonable. No great strength is required for these pieces; and precision tolerance is not a pre-requisite in their sizings. However, the ever-increasing price of such separator slats is encouraging relatively extensive investigation(s) for competitive artificial substitutes; especially those exhibiting the analogous apparent characteristics of the natural materials.
Other traditionally cheap-wood products and fabrications undergoing similar disenchanting experience(s) include: crates and cartons for various fruits and vegetables; large-scale separator or divider sections (as for sorted loadings of less than full capacity quantities of such things as different types of scrap metals, etc., in railway hopper cars, trucks, storage bins, etc.); pallets and palleting (or at least elements thereof); slats and strips for lathing and fencing; construction materials of rustic character; and so forth. For all practical intents, purposes and requirements, such "cheapwood" products seldom, if ever, need to have a tensile strength much, if at all, in excess of about 300 lbs./in.sup.2 (ca. 16 kg/cm.sup.2) or a compressive strength much, if at all, in excess of 240 lbs./in.sup.2 (ca. 12.9 kg/cm.sup.2). Of course, as is obvious, water-resistance in the product is highly desirable for many (especially outdoors) uses.
The use of sawdust as a filler for various binder substitutes seems, at least offhand, to constitute logical possibility for getting at and possibly circumventing the indicated problem. In fact, a fair amount of work has been done and activity expended along this line.
There are, however, at least two significant deleterious drawbacks involved in heretofore known attempts to produce wooden-like articles from sawdust, especially as the commodity has been perforce utilized in prior practice. These include the facts and circumstances that:
(1) The sawdust (or equivalent comminuted cellulosic)particles employed--which typically and usually, despite the fact that exceptions to and variances from the indicated normality, have and are of particulated dimensional characteristics which are on an average particle size reckoning that is ordinarily not much if any more than the No. 10 Size, advantageously less than the No. 12 Size, in the U.S. Sieve Series--must be dried prior to the previously-developed utilizations thereof so as to have an already-standardized and -established maximum moisture content that is between about 3 and about 15 weight percent (i.e., "wt. %"). Now then, "wet" sawdust and the bulk of its equivalent comminuted cellulosic natural plant or "vegetable" couterparts as from undried tree cuttings and other sources (depending on particular species taken and, to some extent, involved location and Season of the taking) has a natural moisture content of from about 40 to about 100 wt. %; a fair average for this being in the neighborhood of 60-70 wt. %. In this connection, the indicated wt. % ranges must be understood and accepted in accordance with the common terminology and definition applied in the trade for given moisture content in such materials. Accordingly and as regards at least "wet" sawdust, the 100 % moisture content level is one which, when equated to an absolute relative constituent parts by weight (i.e., "pbw")basis, means 100 parts of the sawdust and its associated contents as contained in the wood wherefrom it is obtained and 100 pbw water. In other words, the moisture content given is based on that percentage of water in the composition based on and compared to the content of the remaining non-aqueous content(s) of the wood (or the like) from which a given "wet" sawdust lot has been obtained. It is thus readily deducible that (by kiln-drying or the like oven-heating procedures), in order to prepare conventionally-suitable, Specification(s)-meeting, filler-grade sawdust, it is necessary to remove from the "wet" sawdust anywhere from about 97 wt. %, as a maximum, to 35 wt. %, as a minimum, of the original water content of the "wet" starting material to be converted into or incorporated in some sort of desired product. The heat energy required for such water ridding of and from the "wet" sawdust or the like is, quite obviously, enormous; with the expense of same, especially under current conditions and factors of cost for typically-employed fuels, tending to attach almost prohibitive aspects thereabout and thereto.
(2) Binding of dried sawdust and the like filler has only heretofore been with relatively expensive and more or less complex and technically-demanding binder systems, including plastic or resin binders. In illustration of this, reference may be had to the complicated and not uncostly nor uneasy technology involved for such purposes as is disclosed, inter alia, in U.S. Pat. Nos.: 1,642,846; 2,645,587; 2,851,730; 3,309,444; 3,391,038; 3,493,527; 3,554,941; 3,560,255; 3,649,442; 3,787,344; 3,790,401; 3,806,562; 3,956,541; and 4,165,409. As a basically-different curiosity (for present purposes) relating to lightweight brick of clay, sawdust and mortar, see the excerpt identified as "Fin-Times 12-7178, Page 11, CKAR" which appears at Page 12 of the "Technical Survey" for Dec. 23, 1978. Note also Page 1,548 of the "Rubber Handbook" (40th Ed.). A recent typical illustration of the state of the art involved in the binding into fabricated shaped articles of cellulosic materials is to be found in the March 1982 Issue of the International Harvester News (a house organ) which describes the use of dyed straw pressed together into decorative useful objects using resin for the cohesively-binding purpose.This occurs at Page 82 of that Publication which is formally entitled "THE FURROW".
(3) Further to the sort of art mentioned in the above Item (2), reference may be had to the rather comprehensive explanations of various particulated wood products to be found in the 3rd Edition (as well as in earlier compilations) of the famous Kirk-Othmer "Encyclopedia of Chemical Technology" published by John Wiley & Sons, Inc. of New York City. This authoritative source provides definitions of hardboard, particle board, "Masonite" (Reg. TM), insulating board, the so-called dry process board, composition board and so on and so forth; including good descriptions of the method(s) of their respective manufacture--all of which depend more or less on the inclusion and effect for binding of various synthetic resin adhesives, It is noteworthy to observe at Page 377 of Volume 22 of said 3rd Edition the expression as a generality that "wood is seldom used where resistance to chlorine and hypochlorite solution is required".
(4) Additional art of interest illustrating plainly contrsative and diverse techniques for the surface adhesion of and between veneers and/or equivalent layers of pre-formed and already-dried wood structures (whether of not prepared from particulated starting materials) may be found in U.S. Pat. Nos.: 4,007,312 and 4,183,997 which depend for the already-shaped article surface cohesion effect primarily on employment of certain catalysts and conduction of the procedure under generally non-alkaline (or, at least, not pronouncedly alkaline) conditions for the particularized laminating operation which is not adapted to bind together for fabrication into desired structural forms any comminutated and "wet" starting cellulosic materials.
(5) Other art, remotely involved, having no particular bearing on the binding of "wet" sawdust, per se, and/or its communited raw cellulosic likes and equivalents in undried or substantially undried condition and form (e.g., meaning that most if not all of the natural water in the "wet" sawdust, etc., particles being treated remains there at the beginning of the integrally-bonding fabricating procedure) includes U.S. Pat. Nos.: 2,187,016; 2,676,884, 3,536,578 (dealing, by way of particularization, with the addition of an oxidizing agent not reactive with starch to a paperboard material which is sized with starch); 3,859,108; 4,107,379; and 4,234,658 (the last-identified, for example, dealing with the bonding of sub-divided wood or bark wih an adhesive made up of ground-up foliage that has been treated with formaldehyde).
(6) Additionally, the prior art (besides requiring, as has been noted, use of dried sawdust or the like) has almost invariably aimed itself at the capability and desideration of providing: "super"-(as it were)-type goods having high-quality and literally impeccable characteristics as an essential; very good finish and tolerance potential(s); and high strength in the finished, fabricated sawdust and the like or at least analogous particles which are bonded together into composites (such, by way of repeated illustration, as the well-known and already-referred-to phenol-formaldehyde and/or urea-formaldehyde resin-bonded chip and/or particle board and similar manufactures that have gained widespread acceptability and usage in the market).
Despite all above-mentioned and additional which is utilized in and/or known to the art, the possibility of direct usage of "wet" sawdust and/or its likes or equivalents for answer(s) to and solution(s) of the indicated problems appears to have been inadequately addressed and not satisfactorily resolved. This seems to be the case notwithstanding the enigmatic fact that there is a literal superabundance of "wet" sawdust and the like or equivalent fibrous plant cellulosic materials in current available and largely non-utilized supply. In many locations, "wet" sawdust and/or its suitable alternatives can be had for no or little more than handling and/or shipping charges; being unfortunately (and distressingly to possessors thereof) in not great demand. Furthermore and of increasingly significant moment insofar as concerns "wet" sawdust and the like utilization or beneficial disposal or application, environmental restrictions in many locales now prevent burning for fuel purposes (especially on an industrial basis) of such materials.
And, along with these deficiencies, lacks and draw-backs, nothing in applicable prior art appears to realistically concern itself with nor suggest, teach, lead to or provide the instantly-contemplated, unique and estimable compositions and products derived and produced directly from "wet" sawdust or the like in the way so crucially direct and indigenously advantageous as in the present contribution to and advance in the art.